Carrier aggregation (CA) means that a base station configures multiple consecutive or inconsecutive carriers for user equipment (UE), and the UE can perform uplink and downlink transmission simultaneously by using the multiple carriers, so as to increase a data transmission rate. The UE can detect a physical downlink control channel (PDCCH) in a subframe of a carrier, and receive information on a downlink data channel or send information on an uplink data channel according to scheduling information carried on the PDCCH.
In a hybrid automatic repeat request (HARQ) mechanism of a Long Term Evolution (LTE) system, after receiving downlink data that is sent by a base station by using a physical downlink shared channel (PDSCH), UE feeds back a response information codebook on a physical uplink control channel (PUCCH). The response information codebook includes an acknowledgement (ACK) and a negative acknowledgement (NACK). If the UE correctly decodes the downlink data received in a downlink subframe, the UE feeds back an ACK, or if the UE incorrectly decodes the downlink data, the UE feeds back a NACK.
A feedback information sending method in the prior art is generally as follows: A base station configures M carriers in total for UE. When the base station performs scheduling in N downlink subframes of the M carriers, the UE generates ACK/NACK codebooks according to the N downlink subframes of the M carriers, fills a NACK at a position of an ACK/NACK codebook corresponding to a downlink subframe in which scheduling is not performed, and then sends an ACK/NACK codebook on a PUCCH resource in an uplink subframe of a primary carrier.
However, when downlink data occupies only a relatively small part of the N downlink subframes of the M carriers that are configured for the UE, a relatively large quantity of NACKs are filled, due to no scheduling, in the ACK/NACK codebooks that are generated by the UE according to the N downlink subframes of the M carriers. As a result, PUCCH resource utilization is low.